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May 26, 2012

Sturman Cycle Engine Ready to Go

Sturman Industries’ revolutionary engine design and the supporting Sturman cycles that make the camless engine both highly efficient and fuel agnostic are close to being ready for real-world exposure. In a recent two-day Fleet Retreat at the company’s Woodland Park, Colo., headquarters, senior managers of some of the nation’s major truck and bus fleets were shown Sturman’s Air Controlled Engine (ACE) technology, which consists of electronically controlled hydraulic fuel injection and camless inlet and exhaust valve actuation.

The benefits of the technology, which has been under development for two decades since the introduction of the first Sturman fuel injector with digital valve control, include optimized fuel efficiency, emissions compliance with no aftertreatment devices and the ability to burn diesel, natural gas, ethanol and even ammonia with no mechanical changes to the engine.

In fact, no changes are required at all in switching fuels providing the correct injectors are installed for gaseous or liquid fuels. The control system recognizes within one cycle what fuel is being presented and optimizes, through closed-loop control, the injection timing and valve lift and phasing to ideally suit the engine to the fuel.

Because the ACE system is confined to the air and fuel handling, the changes are all in and on the cylinder head, making the technology applicably to any current – or future – medium or heavy-duty diesel.

As part of a tour that preceded the meeting, the visitors were shown the “PIER” engine, a natural-gas fueled Cummins ISX engine – development was funded by the California Energy Commission Public Interest Energy Research program (PIER-08-023).

In this demonstration, Sturman applied the hydraulic unit injectors and hydraulic valve actuation hardware on a modified ISX cylinder head, machined to accept the adaptor plates that mount the valve actuators. A simple, commercially available hydraulic pump added to the belt accessory drive provides the necessary pressure for the actuators and a three-way catalyst cleans up the small emissions in the same way a car’s catalytic converter does.

This engine has run very effectively on the dynamometer and has shown a brake thermal efficiency (BTE) of better than 40% – close to the best diesel efficiency today. This means the converted natural-gas ISX engine offers comparable fuel economy to diesel and emissions that are low enough that it needs no exhaust aftertreatment devices.

The demonstration 15-liter still has the laboratory-style connectors for cooling, fuel, exhaust and so on, but it would take very little to “productionize” these interfaces with the vehicle and the Sturman conversion is ready for prime time.

The object of the Fleet Retreat was to introduce the potential of ACE to some major fleets and garner suggestions for how best to bring the technology to market. To this end, a series of round-table sessions, working in small groups on different aspects of a launch, were held with major feedback from the fleets. Question included: how best to approach the market? what fuel choice would be best? whether the hardware and controls should be introduced as a retrofit to existing engines? and whether an engine or truck original equipment manufacturer should be the launch partner?

And many more . . .

Significant ground was covered in the two-day event and general consensus was arrived at within the working group.

This first retreat’s participants are likely to become the core of an Advisory Group to help bring Sturman Technologies to market. They will likely be the first fleets to bring the technology into their operations, gaining valuable experience with multi-fuel engines, great performance, and fuel economy gains with far fewer troublesome in-engine or external aftertreatment devices.

During the event, it was clear that the fleets accept the emissions changes, and are looking for the technology to meet them without adding significant cost to new vehicles or major increases in maintenance costs.

For more information about ACE, visit For information about upcoming Sturman Fleet Retreats, e-mail Carol Sturman at or Mike Roeth at


  1. And it is likely to be the first to bring fleets and technology in their operations, and get valuable experience with multi-fuel engines, excellent performance, and fuel economy gains much less troublesome in the engine or external aftertreatment devices.

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